1. Field of the Invention
The invention relates to a four post parking platform for motor vehicles, comprising two longitudinally directed platform tracks for receiving the vehicle, a front and rear transverse member which connect the platform tracks to each other and are both guided on their ends at the four posts in a vertical manner, flexible traction cords which are provided for engaging at the transverse members for raising and lowering the platform tracks and can be wound and unwound on spool bodies, a torsionally rigid shaft for connecting the two spool bodies to each other, and with an electrical drive assembly as rotary drive for the spool bodies and the shaft.
Generally, such parking platforms are prepared for use in parking lots, particularly in underground car parks and parking garages, to be able to park two vehicles one above the other on the same floor space. For this purpose, the supporting structure consisting of transverse members and longitudinally directed platform tracks is lowered to the floor level, and by using platform-related ramps a vehicle is driven up onto the platform tracks and secured, for example by applying the parking brake or by using other stopping means, e.g. blocks. The platform tracks are lifted via their transverse members together with the supported motor vehicle by starting the drive motor until they reach an upper parking position. The lift distance is dimensioned such that a sufficiently large space is now available for driving a second motor vehicle under the lifted platform.
2. Description of Related Art
FR-PS-1 050 578 discloses a four post parking platform for two lower and two upper cars wherein two transverse members vertically guided at the four posts are raised and lowered by four traction ropes. In total, four longitudinally directed platform tracks are mounted to the two transverse members, which are used to receive two cars. Two respective lateral posts are connected to a U-shaped frame by a horizontal longitudinal rail at their upper ends. A transverse shaft is mounted to the upper end parts of the two front posts, which carries a coiling drum at each end for simultaneously winding and unwinding a front and a rear traction rope, respectively. A drive assembly is mounted to one of the front posts, which makes the two coiling drums rotate synchronously via the common transverse shaft in order to lift or lower the longitudinally directed platform tracks by means of the traction ropes. In this known parking platform the stationary arrangement of the drive assembly at the upper end of one of the posts is considered a drawback. Furthermore, non-uniform lowering and lifting movements of the platform tracks and thus tilted positions of the vehicles supported thereon may result from the different lengths of the used front and rear traction ropes.
U.S. Pat. No. 2,857,060 discloses a parking garage for cars, having lifting units for the vehicles on several floors. These lifting units are mounted to carriages and supporting frames displaceable on horizontal tracks for transporting the vehicles supported thereon in their lowered positions on a floor into one of the stalls. The supporting frames are lifted and lowered via winches and cables driven by motors.
U.S. Pat. No. 2,233,055 describes a parking platform for two cars each, which is preferably used in garages and by means of which two cars may be parked one above the other. A continuous lifting plate guided on hollow profile posts in a liftable and lowerable manner is used to receive a vehicle. Vertical racks are mounted in the hollow profile posts which engage with rotatingly driven pinions. Two respective pinions are attached to a lateral longitudinal shaft driven on its end by an electric motor.
Finally, a parking garage comprising an integrated lifting platform is disclosed in U.S. Pat. No. 5,335,755. This lifting platform contains two platforms mechanically coupled to each other for receiving two cars. A central motor drives two winch assemblies via transverse shafts, on which a respective traction rope is wound and unwound for lifting and lowering the platform.